Patients are frequently investigated using endoscopic devices in order to diagnose conditions of the stomach which may cause them symptoms. Such conditions may include peptic ulcers, reflux oesophagitis, stomach cancer and lung diseases among other numerous diagnoses.
Oesophagogastro-duodenoscopy, also called gastroscopy, generally requires the patient to: (1) be sedated; (2) have their mouth open by a specialized bite block; and (3) be oxygenated during endoscopy because the procedure sometimes induces hypoxia (low oxygen tension in the blood and tissues). This similarly applies to bronchoscopy as a procedure.
Hypoxia can be of critical importance if the patient does not breathe adequately to maintain oxygen tension, as prolonged low oxygen tension can lead to abnormal heart rhythm, cardiac and respiratory arrest, leading to death. Oxygen tension is currently measured by pulse oximetry and ventilation is achieved by the patient breathing spontaneously as in a deep sleep.
At the clinical level, during endoscopic procedures, every effort is made to ensure sedated patients are adequately ventilated with the aim of oxygen tensions being kept well above 90%. However, due to known patient clinical variability (anatomical differences, such as short neck, inter-current illness, such as emphysema, and past sedative drug use) sedation requirements vary markedly from patient to patient. Hence, it is quite often very difficult, when using higher drug doses, to have the patient adequately sedated and still expect to see spontaneous respiration to a level where the oxygen tension is above 90%. As a result, and not infrequently, patients' oxygen tension dips well below 90% and in some situations patients may end up with respiratory arrest as a complication of endoscopic sedation. Indeed, hypoxia during endoscopy has been referred to by some as ‘Iatrogenic Sleep Apnoea’.
Idiopathic Sleep Apnoea (or Obstructive Sleep Apnoea—OSA) is a common condition in the community where, during sleep, the patient breathes less frequently and/or deeply than the required amount and the oxygen tension can drop to dangerously low levels of even 70% or so, and on rare occasions, down to 55%. Repetitive night apnoea of more than 10 seconds per episode (and up to 2 minutes of apnoea) can be recorded during sleep studies in such patients. These are dangerous levels which can have multiple long term consequences, including hypertension, daytime somnolence, pulmonary hypertension, coronary and cerebrovascular disease and cardiac arrhythmias among others.
During endoscopy or bronchoscopy patients who are ill are being investigated and acute hypoxia induced by sedation which can reproduce ‘sleep apnoea’, can have serious complications including respiratory arrest, cardiac arrest and/or death.
It is therefore of importance to ensure patients are well ventilated and oxygenated, and with airway obstruction prevented wherever possible. On occasions, excessive sedation can induce prolonged apnoea, at times requiring manual ventilation. This is a common enough complication for it to lead to emergency situations and on rare occasions, can result in the death of the patient undergoing an endoscopic examination.
Australian Patent Number 634847 discloses a bite block which oxygenates patients, in order to reduce hypoxic complications of endoscopic sedation. PCT publication no. WO 2001/095971 discloses another oxygenating device, which delivers oxygen mainly via the nose. However, neither of these devices is able to adequately ventilate a patient at a time when he/she is deeply sedated while undergoing often a prolonged procedure. U.S. Pat. No. 6,792,943 discloses a face mask which can ventilate patients for a short time while they are being rapidly intubated. The disclosed mask has two ports, one for intubation of the trachea and another for supply of oxygenation gas under pressure to both nose and mouth. However, given the variability of facial structure and shape, the disclosed mask lacks the ability to obtain a tight enough seal to achieve positive pressure ventilation, which is crucial for intubation.
It is an object of the present invention to substantially overcome or at least ameliorate one or more of the above deficiencies.